$A$ is thrice as good a workman as $B$ and therefore is able to finish a job in $60\, days$ less than $B.$ Working together,they can do it in (in $days$)

$A$ can do a piece of work in $12$ days and $B$ in $15$ days. They work together for $5$ days and then $B$ leaves. The number of days taken by $A$ to finish the remaining work is:

$A$ takes three times as long as $B$ and $C$ together to do a job. $B$ takes four times as long as $A$ and $C$ together to do the work. If all the three,working together,can complete the job in $24$ days,then the number of days $A$ alone will take to finish the job is:

Four examiners can examine a certain number of answer papers in $10$ days by working for $5$ hours a day. For how many hours in a day would $2$ examiners have to work in order to examine twice the number of answer papers in $20$ days?

$A$ alone can complete a work in $18 \, days$ and $B$ alone in $15 \, days.$ $B$ alone worked at it for $10 \, days$ and then left the work. In how many more days will $A$ alone complete the remaining work?

$P$ can complete a work in $12$ days working $8$ hours a day. $Q$ can complete the same work in $8$ days working $10$ hours a day. If both $P$ and $Q$ work together,working $8$ hours a day,in how many days can they complete the work?